1、如何停止一个线程
不要用Thread.stop(),而要像下面这样停止线程,更多信息请看官方文档 https://docs.oracle.com/javase/8/docs/technotes/guides/concurrency/threadPrimitiveDeprecation.html

  private volatile Thread mThread;

 /**
     * 启动线程更新当前日期和时间
     */
    private void startThread() {
        mThread = new Thread(() -> {
            Thread thisThread = Thread.currentThread();
            while (mThread == thisThread ) {
                try {
                    Thread.sleep(1000);
                    Message mesasge = new Message();
                    mesasge.what = 100;
                    mHandler.sendMessage(mesasge);

                } catch (InterruptedException e ) {
                    e.printStackTrace();
                }

            }

            Log.i(TAG, "Thread was stop");

        });
        mThread.start();
    }

    private void updateDatetime() {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy:MM:dd HH:mm:ss");
        datetimeTv.setText(sdf.format(new Date(System.currentTimeMillis())));
    }

    private void stopThread() {
        mThread = null;
    }

2、Java基础：volatile详解